Amyloid positron-emission tomography (PET) improves the diagnosis and treatment of dementia in daily clinical practice, according to results from the ABIDE project

"Previous studies assessing the clinical utility of amyloid imaging used very selected research populations, limiting the translatability to clinical practice," Dr. Arno de Wilde said. "In contrast, we used an unselected memory-clinic cohort, offering amyloid PET to all patients visiting our memory clinic, and for this study, we implemented amyloid PET in our routine diagnostic workup."

In previous studies, the use of amyloid imaging changed the diagnosis of 29% of patients and altered treatment in 64% of cases, Dr. de Wilde and colleagues note in JAMA Neurology, online June 11. But amyloid PET has yet to gain a prominent role in daily clinical practice, they add.

Dr. de Wilde and colleagues evaluated the association of amyloid PET with changes in diagnosis, diagnostic confidence, treatment and patients' experiences in 507 patients.

Amyloid PET was positive in 242 patients (48%), including 78% of those with dementia, 63% of those with mild cognitive impairment (MCI) with suspected Alzheimer dementia (AD) etiology and 25% of patients with MCI of suspected non-AD etiology.

Amyloid PET results were associated with a change in suspected etiological diagnosis for 125 patients (25%), more commonly in patients older than 65 years and significantly more often because of a negative result (31%) then because of a positive result (18%).

Etiological diagnostic confidence increased from 80% to 92% as a result of positive amyloid PET findings and from 79% to 87% as a result of negative scan results (both significant differences).

Treatment changed for 24% of patients after the amyloid PET, significantly more often after a positive scan than after a negative scan. Scan results also led to changes in patient treatment for 11% of those with subjective cognitive decline. Anxiety levels in patients did not increase or decrease after the amyloid PET, regardless of whether the result was positive or negative.

"I think that our results demonstrate that amyloid PET can be a very useful tool in daily clinical practice," Dr. de Wilde said. "In addition, we show preliminary evidence that disclosing results in actual practice doesn't seem to be harmful to patients. Clinicians could use these results to support their clinical use of the amyloid PET."

"However, and of equal importance, our results also show that not all patients visiting a memory clinic benefit from the amyloid PET," he said. "Within that context, I think it is very important for clinicians to select patients for an amyloid PET where the chance of having a clinical impact is the greatest."

Diagnostic accuracy

Dr. Stephen Salloway from Alpert Medical School of Brown University told, "Alzheimer's disease is frequently misdiagnosed. Amyloid PET is a reliable and safe measure of amyloid plaques in the brain that improves diagnostic accuracy. This test provides doctors with important information to guide treatment and helps patients and families dealing with cognitive impairment make important decisions."

"Though approved by the FDA, the use of amyloid PET is limited by a lack of insurance coverage," said Dr. Salloway, who was not involved in the new work. "Hopefully, the results of this paper and other large-scale trials currently underway will lead to greater availability of amyloid PET in clinical practice."

Dr. Perry, who also was not involved in the new work, said the findings, and those from earlier studies "help us focus on new areas of interest, particularly, the benefits and risks of knowing amyloid status in those with subjective cognitive complaints and the more elderly amnestic group of patients who may be amyloid negative and have a more benign prognosis."

He added, "I think that the assessment of anxiety and uncertainty helps reassure our clinical intuition that our patients are often looking for clarity and that reaching that clarity is helpful rather than anxiety provoking."

"I think this is particularly relevant to those with only subjective cognitive impairment, who currently sit outside the licensing applications of these PET agents in clinical practice, but will, with more longitudinal follow-up data, become an increasing focus of an investigation."